Catheter having mapping assembly

ABSTRACT

A catheter that is particularly useful for mapping tubular regions of the heart, such as the pulmonary vein, is provided. The catheter comprises an elongated tubular catheter body having an outer wall, proximal and distal ends, and at least one lumen extending therethrough. The catheter further includes a mapping assembly, which comprises a tubular structure comprising a generally circular main region generally transverse and distal to the catheter body and having an outer circumference and a generally straight distal region distal to the main region, wherein the tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A support member having shape-memory is disposed within at least the main region of the mapping assembly. A plurality of electrode pairs, each comprising two ring electrodes, are carried by the generally circular main region of the mapping assembly.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/551,467, filed Apr. 17, 2000, which claims the benefit ofU.S. Provisional Application No. 60/178,478, filed Jan. 27, 2000, theentire disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to an improved mapping catheterthat is particularly useful for mapping electrical activity in a tubularregion of or near the heart.

BACKGROUND OF THE INVENTION

[0003] Atrial fibrillation is a common sustained cardiac arrhythmia anda major cause of stroke. This condition is perpetuated by reentrantwavelets propagating in an abnormal atrial-tissue substrate. Variousapproaches have been developed to interrupt wavelets, including surgicalor catheter-mediated atriotomy. Prior to treating the condition, one hasto first determine the location of the wavelets. Various techniques havebeen proposed for making such a determination. None of the proposedtechniques, however, provide for measurement of the activity within apulmonary vein, coronary sinus or other tubular structure about theinner circumference of the structure.

SUMMARY OF THE INVENTION

[0004] The present invention is directed to a catheter having a mappingassembly and a method for measuring electrical activity within a tubularregion of or near the heart, e.g., a pulmonary vein, the coronary sinus,the superior vena cava, or the pulmonary outflow tract. The mappingassembly, which has a generally circular region with a series ofspaced-apart electrodes mounted thereon, is positioned within thetubular region so that the electrodes are in contact with an innergenerally circumferential surface inside the tubular structure.

[0005] In one embodiment, the invention is directed to a mappingcatheter comprising an elongated tubular catheter body and a mappingassembly mounted at the distal end of the catheter body. The catheterbody has an outer wall, proximal and distal ends, and at least one lumenextending therethrough. The mapping assembly comprises a tubularstructure comprising a generally circular main region generallytransverse and distal to the catheter body and having an outercircumference and a generally straight distal region distal to the mainregion. The tubular structure comprises a non-conductive cover over atleast the main region of the mapping assembly. A support member havingshape-memory is disposed within at least the main region of the mappingassembly. A plurality of electrode pairs, each comprising two ringelectrodes, are carried by the generally circular main region of themapping assembly.

[0006] In another embodiment, the invention is directed to a mappingcatheter comprising an elongated tubular catheter body and a mappingassembly mounted at the distal end of the catheter body. The catheterbody has an outer wall, proximal and distal ends, and at least one lumenextending therethrough. The mapping assembly comprises a tubularstructure comprising a generally circular main region generallytransverse and distal to the catheter body and having an outercircumference and a generally straight distal region distal to the mainregion. The tubular structure comprises a non-conductive region over atleast the main region of the mapping assembly. A plurality of electrodepairs, each comprising two ring electrodes, are carried by the generallycircular main region of the mapping assembly. One ring electrode has alength ranging from about 1 mm to about 1.5 mm, and all of the otherring electrodes each have a length ranging from about 0.4 mm to about0.75 mm.

[0007] In another embodiment, the invention is directed to a mappingcatheter comprising an elongated tubular catheter body and a mappingassembly mounted at the distal end of the catheter body. The catheterbody has an outer wall, proximal and distal ends, and at least one lumenextending therethrough. The mapping assembly comprises a tubularstructure having a generally circular main region generally transverseand distal to the catheter body having an outer circumference. Thetubular structure comprises a non-conductive cover over at least themain region of the mapping assembly. A support member havingshape-memory is disposed within at least the main region of the mappingassembly. A plurality of electrode pairs are carried by the generallycircular main region of the mapping assembly. The catheter furthercomprises means for deflecting the distal end of the catheter bodywithout altering the shape of the mapping assembly.

[0008] In another embodiment, the invention is directed to a mappingcatheter comprising an elongated tubular catheter body and a mappingassembly mounted at the distal end of the catheter body. The catheterbody has an elongated flexible tubular catheter body having an axis andproximal and distal ends. The mapping assembly has a preformed generallycircular curve having an outer surface, is generally transverse to theaxis of the catheter body, and carries a plurality of electrode pairs.An electrode lead wire is associated with each electrode. Each electrodelead wire extends through the catheter body and into the mappingassembly. The distal end of each electrode lead wire is electricallyconnected to its associated electrode. The catheter further includes apuller wire and handle for deflection of the distal end of the catheterbody. The puller wire extends through the tubular catheter body. Thedistal end of the puller wire is fixedly attached to the distal end ofthe catheter body. The handle is connected to the proximal ends of thecatheter body and puller wire for moving the puller wire longitudinallyrelative to the catheter body, whereby longitudinal movement of thepuller wire relative to the catheter body results in deflection of thedistal end of the catheter body.

[0009] In another embodiment, the invention is directed to a method formapping electrical activity within a tubular region of or near the hearthaving a inner circumference. The method comprises inserting the distalend of a catheter as described above into the heart, contacting theouter circumference of the generally circular main region with the innercircumference of the tubular region, and mapping the electrical activitywithin the tubular region with the electrodes along the generallycircular main region. The method is particularly useful for mappingtubular regions such as pulmonary veins, the coronary sinus, thesuperior vena cava, and the pulmonary outflow tract.

DESCRIPTION OF THE DRAWINGS

[0010] These and other features and advantages of the present inventionwill be better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings wherein:

[0011]FIG. 1 is a side cross-sectional view of an embodiment of thecatheter of the invention.

[0012]FIG. 2 is a side cross-sectional view of a catheter body accordingto the invention, including the junction between the catheter body andintermediate section.

[0013]FIG. 3 is a cross-sectional view of the intermediate section,including the junction between the intermediate section and the mappingassembly.

[0014]FIG. 4 is a schematic perspective view of the mapping assemblyaccording to the invention.

[0015]FIG. 5 is a side view of the mapping assembly according to theinvention in a clockwise formation.

[0016]FIG. 6 is a side view of the mapping assembly according to theinvention in a counterclockwise formation rotated 90° relative to theassembly depicted in FIG. 5.

[0017]FIG. 7 is a schematic view of the mapping assembly according tothe invention.

[0018]FIG. 8 is a schematic view of the mapping assembly according tothe invention depicting the relationship between the first and lastelectrodes.

[0019]FIG. 9 is a schematic view of an alternative mapping assemblyaccording to the invention.

DETAILED DESCRIPTION

[0020] In a particularly preferred embodiment of the invention, there isprovided a catheter having a mapping assembly at its distal end. Asshown in FIG. 1, the catheter comprises an elongated catheter body 12having proximal and distal ends, a intermediate section 14 at the distalend of the catheter body, a control handle 16 at the proximal end of thecatheter body, and a mapping assembly 17 mounted at the distal end ofthe catheter to the intermediate section.

[0021] With reference to FIG. 2, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 comprises an imbedded braided mesh ofstainless steel or the like to increase torsional stiffness of thecatheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 will rotate in acorresponding manner.

[0022] The outer diameter of the catheter body 12 is not critical, butis preferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate a puller wire, leadwires, and any other desired wires, cables or tubes. If desired, theinner surface of the outer wall 20 is lined with a stiffening tube (notshown) to provide improved torsional stability. A particularly preferredcatheter has an outer wall 20 with an outer diameter of from about 0.090inch to about 0.94 inch and an inner diameter of from about 0.061 inchto about 0.065 inch.

[0023] The intermediate section 14 comprises a short section of tubing22 having three lumens. The first lumen 30 electrode carries lead wires50, the second lumen 32 carries a puller wire 64, and the third lumen 34carries a support member 24. The tubing 22 is made of a suitablenontoxic material that is preferably more flexible than the catheterbody 12. A presently preferred material for the tubing 22 is braidedpolyurethane, i.e., polyurethane with an embedded mesh of braidedstainless steel or the like. The size of each lumen is not critical, butis sufficient to house the lead wires, puller wire or support member.

[0024] The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the mapping assembly 17, can vary asdesired. Preferably the useful length ranges from about 110 cm to about120 cm. The length of the intermediate section 14 is a relatively smallportion of the useful length, and preferably ranges from about 3.5 cm toabout 10 cm, more preferably 6 from about 5 cm to about 6.5 cm.

[0025] A preferred means for attaching the catheter body 12 to theintermediate section 14 is illustrated in FIG. 2. The proximal end ofthe intermediate section 14 comprises an outer circumferential notch 26that receives the inner surface of the outer wall 22 of the catheterbody 12. The intermediate section 14 and catheter body 12 are attachedby glue or the like.

[0026] If desired, a spacer (not shown) can be located within thecatheter body between the distal end of the stiffening tube (ifprovided) and the proximal end of the intermediate section. The spacerprovides a transition in flexibility at the junction of the catheterbody and intermediate section, which allows this junction to bendsmoothly without folding or kinking. A catheter having such a spacer isdescribed in U.S. Pat. No. 5,964,757, the disclosure of which isincorporated herein by reference.

[0027] At the distal end of the intermediate section 14 is a mappingassembly, as shown in FIGS. 3 to 7. The mapping assembly is formed fromthe distal end of the support member 24 covered by a non-conductivecovering 28. The mapping assembly comprises a generally straightproximal region 38, a generally circular main region and a generallystraight distal region 40. The proximal region 38 is mounted on theintermediate section 14, as described in more detail below, so that itsaxis is generally parallel to the axis of the intermediate section. Theproximal region 38 preferably has an exposed length, e.g., not containedwithin the intermediate section 14, ranging from about 3 mm to about 12mm, more preferably about 3 mm to about 8 mm, still more preferablyabout 5 mm inch, but can vary as desired.

[0028] The generally circular main region 39 does not form a flatcircle, but is very slightly helical, as shown in FIGS. 4 to 6. The mainregion 39 has an outer diameter preferably ranging to about 10 mm toabout 25 mm, more preferably about 12 mm to about 20 mm, still morepreferably about 15 mm. The transition region 41 of the straightproximal region 38 and generally circular main region 39 is slightlycurved and formed such that, when viewed from the side with the proximalregion at the top of the circular main region as shown in FIG. 5, theproximal region (along with the intermediate section 14) forms an angleα with the curved region ranging from about 75° to about 95°, preferablyfrom about 83° to about 93°, more preferably about 87°. The main region39 can curve in a clockwise direction, as shown in FIG. 5, or acounterclockwise direction, as shown in FIG. 6. When the assembly 17 isturned 90°, as shown in FIG. 6, so that the transition region 41 is nearthe center of the main region, the proximal region (along with theintermediate section 14) forms an angle β with the main region rangingfrom about 90° to about 135°, preferably from about 100° to about 110°,more preferably about 105°.

[0029] The support member 24 is made of a material having shape-memory,i.e., that can be straightened or bent out of its original shape uponexertion of a force and is capable of substantially returning to itsoriginal shape upon removal of the force. A particularly preferredmaterial for the support member 24 is a nickel/titanium alloy. Suchalloys typically comprise about 55% nickel and 45% titanium, but maycomprise from about 54% to about 57% nickel with the balance beingtitanium. A preferred nickel/titanium alloy is Nitinol, which hasexcellent shape memory, together with ductility, strength, corrosionresistance, electrical resistivity and temperature stability. Thenon-conductive covering 28 can be made of any suitable material, and ispreferably made of a biocompatible plastic such as polyurethane orPEBAX.

[0030] A series of ring electrodes 36 are mounted on the non-conductivecovering 28 of the generally circular main region 39 of the mappingassembly 17. The ring electrodes 36 can be made of any suitable solidconductive material, such as platinum or gold, preferably a combinationof platinum and iridium, and mounted onto the non-conductive covering 28with glue or the like. Alternatively, the ring electrodes can be formedby coating the non-conductive covering 28 with an electricallyconducting material, like platinum, gold and/or iridium. The coating canbe applied using sputtering, ion beam deposition or an equivalenttechnique.

[0031] In a preferred embodiment, each ring electrode 36 is mounted byfirst forming a hole in the non-conductive covering 28. An electrodelead wire 50 is fed through the hole, and the ring electrode 36 iswelded in place over the lead wire and non-conductive covering 28. Thelead wires 50 extend between the non-conductive covering 28 and thesupport member 24. The proximal end of each lead wire 50 is electricallyconnected to a suitable connector 37, which is connected to a source ofRF energy (not shown).

[0032] The number of ring electrodes 36 on the assembly can vary asdesired. Preferably the number of ring electrodes ranges from about sixto about twenty, preferably from about eight to about twelve. In aparticularly preferred embodiment, the assembly carries ten ringelectrodes. The ring electrodes 36 are preferably approximately evenlyspaced around the generally circular main region 39, as best shown inFIG. 7. In a particularly preferred embodiment, a distance ofapproximately 5 mm is provided between the centers of the ringelectrodes 36.

[0033]FIGS. 7 and 8 show a particularly preferred electrode arrangement.As explained above, the generally circular main region 39 is veryslightly helical, although FIGS. 7 and 8 depict the main region as aflat circle, as it would generally appear when viewed from the distalend of the catheter. The generally straight distal region 40 forms atangent relative to the generally circular main region 39 and contactsthe main region at a tangent point 43. A first electrode 36 a isprovided, which is the electrode that is on the generally circular mainregion 39 closest to the proximal region 38. A second electrode 36 b isprovided, which is the electrode that is on the generally circular mainregion 39 closest to the distal region 40. Preferably, the firstelectrode 36 a is positioned along the circumference of the generallycircular main region 39 at a distance 0 of no more than about 55° fromthe tangent point, more preferably no more than about 48° from thetangent point, still more preferably from about 15° to about 36° fromthe tangent point. Preferably the second electrode 36 b is positionedalong the circumference of the generally circular main region 39 at adistance ω of no more than about 55° degrees from the tangent point,more preferably no more than about 48° from the tangent point, stillmore preferably from about 15° to about 36° from the tangent point.Preferably the first electrode 36 a is positioned along thecircumference of the generally circular main region 39 at a distance γof no more than 100° from the second electrode 36 b, preferably no morethan 80° from the second electrode, still more preferably from about 30°to about 75° from the second electrode.

[0034] An alternative electrode arrangement is depicted in FIG. 9. Inthis embodiment, the mapping assembly includes a series of ringelectrode pairs 35. Each ring electrode pair 35 comprises twoclosely-spaced ring electrodes 36. As used herein, the term “ringelectrode pair” refers to a pair of ring electrodes that are arrangedcloser to each other than they are to the other adjacent ringelectrodes. Preferably the distance between two electrodes 36 of anelectrode pair 35 is less than about 3 mm, more preferably less thanabout 2 mm, still more preferably from about 0.5 mm to about 1.5 mm. Thenumber of electrode pairs 35 can vary as desired, and preferably rangesfrom 6 to 14 pairs, more preferably 10 pairs.

[0035] In a particularly preferred embodiment, the mapping assemblycarries 10 pairs of electrodes with a space of approximately 1 mmbetween the two electrodes 36 of each pair 35. Preferably each ringelectrode 36 is relatively short, having a length ranging from about 0.4mm to about 0.75 mm, with the most distal ring electrode 36 c beinglonger than the other ring electrodes, preferably having a lengthranging from about 1 mm to about 1.5 mm. The longer ring electrodeprovides a signal to the user when the catheter is being viewed underfluoroscopy. Specifically, because the mapping assembly is generallycircular, it can be difficult for the user to determine which electrodesare placed at a particular location in the heart. By having one ringelectrode, such as the most distal ring electrode, sized differentlyfrom the other ring electrodes, the user has a reference point whenviewing the catheter under fluoroscopy.

[0036] Regardless of the size and number of the ring electrodes 36, theelectrode pairs 35 are preferably approximately evenly spaced around thegenerally circular main region 39. The closely-spaced electrode pairs 35allow for more accurate detection of near field pulmonary vein potentialversus far field atrial signals, which is very important when trying totreat atrial fibrillation. Specifically, the near field pulmonary veinpotentials are very small signals whereas the atria, located very closeto the pulmonary vein, provides much larger signals. Accordingly, evenwhen the mapping array is placed in the pulmonary vein, it can bedifficult for the physician to determine whether the signal is a small,close potential (from the pulmonary vein) or a larger, farther potential(from the atria). Closely-spaced bipoles permit the physician to moreaccurately determine whether he is looking at a close signal or a farsignal. Accordingly, by having closelyspaced electrodes, one is able totarget exactly the locations of myocardial tissue that have pulmonaryvein potentials and therefore allows the clinician to deliver therapy tothe specific tissue. Moreover, the closely-spaced electrodes allow thephysician to determine the exact anatomical location of the ostium bythe electrical signal.

[0037] If desired, additional electrodes (not shown) could be mountedalong the intermediate section 14, the generally straight proximalsection 39, the transition region 41, and generally straight distalregion 40.

[0038] The generally straight distal region 40 is provided with anatraumatic design to prevent the distal end of the mapping assembly 17from penetrating tissue. In the depicted embodiment, the distal region40 comprises a tightly wound coil spring 44 made, for example, ofstainless steel, such as the mini guidewire commercially available fromCordis Corporation (Miami, Fla.) or a coil having a 0.0045 inch wiresize and a 0.009 inch inner diameter, such as that commerciallyavailable from Microspring. The coil spring 44 is mounted at itsproximal end in a short piece of tubing 45 with polyurethane glue or thelike, which is then glued or otherwise anchored within thenon-conductive covering 28. The tubing 45 is less flexible than thenonconductive covering 28 but more flexible than that support member 24to provide a transition in flexibility along the length of the mappingassembly 17. The distal end of the distal region 40 is capped,preferably with polyurethane glue 46, to prevent body fluids fromentering the mapping assembly 17. In the depicted embodiment, thegenerally straight distal region 40 has a length of about 0.5 inch, butcan be any desired length, for example, ranging from about 0.25 inch toabout 1.0 inch. The generally straight distal region 40 is preferablysufficiently long to serve as an anchor for introducing the catheterinto a guiding sheath, as discussed in more detail below, because themapping assembly 17 must be straightened upon introduction into thesheath. Without having the generally straight distal region 40 as ananchor, the mapping assembly 17 has a tendency to pull out of theguiding sheath upon its introduction into the guiding sheath. Any otheratraumatic tip design that prevents the distal end of the mappingassembly from penetrating tissue could be provided. An alternativedesign in the form of a plastic ball is described in copending patentapplication Ser. No. 09/370,605, entitled “ATRIAL BRANDING IRON CATHETERAND METHOD FOR TREATING ATRIAL FIBRILLATION”, the entire disclosure ofwhich is incorporated herein by reference. Additionally, if desired, thedistal region 40 can be formed, at least in part, of a radiopaquematerial to aid in the positioning of the mapping assembly 17 underfluoroscopy.

[0039] The junction of the intermediate section 14 and mapping assembly17 is shown in FIG. 3. The non-conductive covering 28 is attached to thetubing 22 of the intermediate section by glue or the like. The supportmember 24 extends from the third lumen 32 into the nonconductivecovering 28. The proximal end of the support member 24 terminates ashort distance within the third lumen 32, approximately about 5 mm, soas not to adversely affect the ability of the intermediate section 14 todeflect. However, if desired, the proximal end of the support member 24can extend into the catheter body 12.

[0040] The lead wires 50 attached to the ring electrodes 36 extendthrough the first lumen 30 of the intermediate section 14, through thecentral lumen 18 of the catheter body 12, and the control handle 16, andterminate at their proximal end in the connector 37. The portion of thelead wires 50 extending through the central lumen 18 of the catheterbody 12, control handle 16 and proximal end of the intermediate section14 are enclosed within a protective sheath 62, which can be made of anysuitable material, preferably polyimide. The protective sheath 62 isanchored at its distal end to the proximal end of the intermediatesection 14 by gluing it in the first lumen 30 with polyurethane glue orthe like.

[0041] The puller wire 64 is provided for deflection of the intermediatesection 14. The puller wire 64 extends through the catheter body 12, isanchored at its proximal end to the control handle 16, and is anchoredat its distal end to the intermediate section 14. The puller wire 64 ismade of any suitable metal, such as stainless steel or Nitinol, and ispreferably coated with Teflon® or the like. The coating impartslubricity to the puller wire 64. The puller wire 64 preferably has adiameter ranging from about 0.006 to about 0.010 inch.

[0042] A compression coil 66 is situated within the catheter body 12 insurrounding relation to the puller wire 64. The compression coil 66extends from the proximal end of the catheter body 12 to the proximalend of the intermediate section 14. The compression coil 66 is made ofany suitable metal, preferably stainless steel. The compression coil 66is tightly wound on itself to provide flexibility, i.e., bending, but toresist compression. The inner diameter of the compression coil 66 ispreferably slightly larger than the diameter of the puller wire 64. TheTeflon® coating on the puller wire 64 allows it to slide freely withinthe compression coil 66. The outer surface of the compression coil 66 iscovered by a flexible, non-conductive sheath 68, e.g., made of polyimidetubing.

[0043] The compression coil 66 is anchored at its proximal end to theouter wall 20 of the catheter body 12 by proximal glue joint 70 and atits distal end to the intermediate section 14 by distal glue joint 72.Both glue joints 70 and 72 preferably comprise polyurethane glue or thelike. The glue maybe applied by means of a syringe or the like through ahole made between the outer surface of the catheter body 12 and thecentral lumen 18. Such a hole may be formed, for example, by a needle orthe like that punctures the outer wall 20 of the catheter body 12 whichis heated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil66 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of the compression coil.

[0044] The puller wire 64 extends into the second lumen 32 of theintermediate section 14. Preferably the puller wire 64 is anchored atits distal end to the distal end of the intermediate section 14, asshown in FIG. 3. Specifically, a T-shaped anchor is formed, whichcomprises a short piece of tubular stainless steel 80, e.g., hypodermicstock, which is fitted over the distal end of the puller wire 64 andcrimped to fixedly secure it to the puller wire. The distal end of thetubular stainless steel 80 is fixedly attached, e.g., by welding, to across-piece 82 formed of stainless steel ribbon or the like. Thecross-piece 82 sits beyond the distal end of the second lumen 32. Thecross-piece 82 is larger than the lumen opening and, therefore, cannotbe pulled through the opening. The distal end of the second lumen 32 isthen filled with glue or the like, preferably a polyurethane glue.Within the second lumen 32 of the intermediate section 14, the pullerwire 64 extends through a plastic, preferably Teflon®, puller wiresheath (not shown), which prevents the puller wire 64 from cutting intothe wall of the intermediate section 14 when the intermediate section isdeflected.

[0045] Longitudinal movement of the puller wire 42 relative to thecatheter body 12, which results in deflection of the intermediatesection 14, is accomplished by suitable manipulation of the controlhandle 16. Examples of suitable control handles for use in the presentinvention are disclosed, for example, in U.S. Pat. Nos. Re 34,502 and5,897,529, the entire disclosures of which are incorporated herein byreference.

[0046] In use, a suitable guiding sheath is inserted into the patientwith its distal end positioned at a desired mapping location. An exampleof a suitable guiding sheath for use in connection with the presentinvention is the Preface™ Braiding Guiding Sheath, commerciallyavailable from Cordis Webster (Diamond Bar, Calif.). The distal end ofthe sheath is guided into one of the atria. A catheter in accordancewith the present invention is fed through the guiding sheath until itsdistal end extends out of the distal end of the guiding sheath. As thecatheter is fed through the guiding sheath, the mapping assembly 17 isstraightened to fit through the sheath. Once the distal end of thecatheter is positioned at the desired mapping location, the guidingsheath is pulled proximally, allowing the deflectable intermediatesection 14 and mapping assembly 17 to extend outside the sheath, and themapping assembly 17 returns to its original shape due to theshape-memory of the support member 24. The mapping assembly 17 is theninserted into a pulmonary vein or other tubular region (such as thecoronary sinus, superior vena cava, or inferior vena cava) so that theouter circumference of the generally circular main region 39 of theassembly is in contact with a circumference inside the tubular region.Preferably at least about 50%, more preferably at least about 70%, andstill more preferably at least about 80% of the circumference of thegenerally circular main region is in contact with a circumference insidethe tubular region.

[0047] The circular arrangement of the electrodes 36 permits measurementof the electrical activity at that circumference of the tubularstructure so that ectopic beats between the electrodes can beidentified. The size of the generally circular main region 39 permitsmeasurement of electrical activity along a diameter of a pulmonary veinor other tubular structure of or near the heart because the circularmain region has a diameter generally corresponding to that of apulmonary vein or the coronary sinus. Additionally, because the mainregion 39 preferably does not form a flat circle, but instead issomewhat helical, as shown in FIG. 4, it is easier for the user to guidethe mapping assembly 17 into a tubular region.

[0048] If desired, two or more puller wires can be provided to enhancethe ability to manipulate the intermediate section. In such anembodiment, a second puller wire and a surrounding second compressioncoil extend through the catheter body and into an additional off-axislumen in the intermediate section. The first puller wire is preferablyanchored proximal to the anchor location of the second puller wire.Suitable designs of catheters having two or more puller wires, includingsuitable control handles for such embodiments, are described, forexample, in U.S. patent application Ser. No. 08/924,611, filed Sep. 5,1997; Ser. No. 09/130,359, filed Aug. 7, 1998; Ser. No. 09/143,426,filed Aug. 28, 1998; and Ser. No. 09/157,055, filed Sep. 18, 1998, thedisclosures of which are incorporated herein by reference.

[0049] The preceding description has been presented with reference topresently preferred embodiments of the invention. Workers skilled in theart and technology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

[0050] Accordingly, the foregoing description should not be read aspertaining only to the precise structures described and illustrated inthe accompanying drawings, but rather should be read consistent with andas support to the following claims which are to have their fullest andfair scope.

1. A mapping catheter comprising: an elongated tubular catheter bodyhaving an outer wall, proximal and distal ends, and at least one lumenextending therethrough; and a mapping assembly comprising: a tubularstructure comprising a generally circular main region generallytransverse and distal to the catheter body and having an outercircumference and a generally straight distal region distal to the mainregion, wherein the tubular structure comprises a nonconductive coverover at least the main region of the mapping assembly, a support memberhaving shape-memory disposed within at least the main region of themapping assembly, and a plurality of electrode pairs, each comprisingtwo ring electrodes, carried by the generally circular main region ofthe mapping assembly.
 2. A catheter according to claim 1, wherein themapping assembly further comprises a generally straight proximal regionattached to the catheter body and a transition region connecting theproximal region and the main region.
 3. A catheter according to claim 1,wherein the generally circular main region has an outer diameter rangingto about 10 mm to about 25 mm.
 4. A catheter according to claim 1,wherein the generally circular main region has an outer diameter rangingto about 12 mm to about 20 mm.
 5. A catheter according to claim 1,wherein the number of ring electrode pairs along the generally circularmain region ranges from about six to about fourteen.
 6. A catheteraccording to claim 1, comprising ten ring electrode pairs along thegenerally circular main region.
 7. A catheter according to claim 1,wherein the ring electrode pairs are approximately evenly spaced aroundthe generally circular main region.
 8. A catheter according to claim 1,wherein the distance between two ring electrodes of each ring electrodepair is less than about 3 mm.
 9. A catheter according to claim 1,wherein the distance between two ring electrodes of each ring electrodepair is less than about 2 mm.
 10. A catheter according to claim 1,wherein the distance between two ring electrodes of each ring electrodepair ranges from about 0.5 mm to about 1.5 mm.
 11. A catheter accordingto claim 1, wherein at least some of the ring electrodes of theelectrode pairs have a length ranging from about 0.4 mm to about 0.75mm.
 12. A catheter according to claim 1, wherein one ring electrode hasa length longer than the length of the other ring electrodes.
 13. Acatheter according to claim 1, wherein one ring electrode has a lengthranging from about 1 mm to about 1.5 mm and all of the other ringelectrodes each having a length ranging from about 0.4 mm to about 0.75mm.
 14. A catheter according to claim 1, wherein the generally straightdistal region has an atraumatic design to prevent the distal end of themapping assembly from penetrating tissue.
 15. A catheter according toclaim 1, further comprising means for deflecting the distal end of thecatheter body without altering the shape of the mapping assembly.
 16. Acatheter according to claim 15, wherein the deflecting means comprises:a puller wire extending through a lumen of the catheter body, saidpuller wire being fixedly attached at its distal end to the catheterbody near the catheter body's distal end; and a control handle formoving the puller wire longitudinally relative to the catheter body tothereby cause deflection of the distal end of the catheter body.
 17. Acatheter according to claim 1, wherein the distal region is moreflexible than the main region.
 18. A catheter according to claim 1,wherein the transition region is slightly curved and formed such that,when viewed from the side of the catheter with the proximal region atthe top of the circular main region, the proximal region forms an anglea with the circular region ranging from about 75° to about 95°.
 19. Acatheter according to claim 1, wherein the transition region is slightlycurved and formed such that, when viewed from the side of the catheterwith the proximal region at the top of the circular main region, theproximal region forms an angle a with the circular main region rangingfrom about 83° to about 93°.
 20. A mapping catheter comprising: anelongated tubular catheter body having an outer wall, proximal anddistal ends, and at least one lumen extending therethrough; and amapping assembly comprising: a tubular structure comprising a generallycircular main region generally transverse and distal to the catheterbody and having an outer circumference and a generally straight distalregion distal to the main region, wherein the tubular structurecomprises a nonconductive region over at least the main region of themapping assembly, and a plurality of electrode pairs, each comprisingtwo ring electrodes, carried by the generally circular main region ofthe mapping assembly, wherein one ring electrode has a length rangingfrom about 1 mm to about 1.5 mm and all of the other ring electrodeseach having a length ranging from about 0.4 mm to about 0.75 mm.
 21. Acatheter according to claim 20, wherein the one ring electrode having alength ranging from about 1 mm to about 1.5 mm is positioned on themapping assembly distal to all of the other ring electrodes on themapping assembly.
 22. A mapping catheter comprising: an elongatedtubular catheter body having an outer wall, proximal and distal ends,and at least one lumen extending therethrough; a mapping assemblycomprising: a tubular structure having a generally circular main regiongenerally transverse and distal to the catheter body having an outercircumference, wherein the tubular structure comprises a non-conductivecover over at least the main region of the mapping assembly, a supportmember having shape-memory disposed within at least the main region ofthe mapping assembly, and a plurality of electrode pairs carried by thegenerally circular main region of the mapping assembly; and means fordeflecting the distal end of the catheter body without altering theshape of the mapping assembly.
 23. A catheter comprising: an elongatedflexible tubular catheter body having an axis and proximal and distalends; a mapping assembly at the distal end of the tubular body having apreformed generally circular curve having an outer surface, beinggenerally transverse to the axis of the catheter body, and havingproximal and distal ends and carrying a plurality of electrode pairs; anelectrode lead wire associated with each electrode, each electrode leadwire having proximal and distal ends and extending through the catheterbody and into the mapping assembly, the distal end of each electrodelead wire being electrically connected to its associated electrode; apuller wire having proximal and distal ends extending through thetubular catheter body, the distal end of the puller wire being fixedlyattached to the distal end of the catheter body; and a handle connectedto the proximal ends of the catheter body and puller wire for moving thepuller wire longitudinally relative to the catheter body, wherebylongitudinal movement of the puller wire relative to the catheter bodyresults in deflection of the distal end of the catheter body.
 24. Amethod for mapping electrical activity within a tubular region of ornear the heart having a inner circumference, the method comprising:inserting the distal end of a catheter according to claim 1 into theheart; contacting the outer circumference of the generally circular mainregion with the inner circumference of the tubular region; and mappingthe electrical activity within the tubular region with the electrodesalong the generally circular main region.
 25. A method according toclaim 24, wherein the tubular region is selected from the groupconsisting of pulmonary veins, the coronary sinus, the superior venacava, and the inferior vena cava.
 26. A method according to claim 24,wherein the tubular region is a pulmonary vein.
 27. A method accordingto claim 24, wherein the generally circular main region has an outerdiameter ranging to about 12 mm to about 20 mm.
 28. A method accordingto claim 24, wherein the number of ring electrode pairs along thegenerally circular main region ranges from about six to about fourteen.29. A method according to claim 24, comprising ten ring electrode pairsalong the generally circular main region, wherein the distance betweentwo ring electrodes of each ring electrode pair is less than about 2 mm.30. A method according to claim 24, wherein the distance between tworing electrodes of each ring electrode pair ranges from about 0.5 mm toabout 1.5 mm.
 31. A method according to claim 24, wherein at least about50% of the outer circumference of the generally circular main region isin contact with the inner circumference of the tubular region.
 32. Amethod according to claim 24, wherein at least about 80% of the outercircumference of the generally circular main region is in contact withthe inner circumference of the tubular region.